The Benefits and Dangers of Genetic Engineering in Agriculture

By Ryan Shon

November 17, 2001

During the past three decades, developments in molecular biology have enabled scientists to genetically alter, or "engineer" organisms. This technology has been applied to agriculture, giving crops new abilities such as resistance to insect pests, and even enhanced nutritional value. While genetically engineered crops have the potential to revolutionize agriculture, they also cause unacceptable health and environmental hazards. Because of this, the development and use of genetically engineered plants should not be permitted.

Genetic engineering allows new plants to be developed with new, advantageous and exotic characteristics that could not be added by the conventional methods of breeding. In breeding, plants which display superior characteristics are selected and mated together to produce offspring with the traits of the parents. Other, more exotic methods of breeding using cell cultures and mutagenic agents have been developed as well (McHughen 64, 65). Breeding, however, always involves mating individual organisms to produce a new plant, and breeders are limited in what traits can be added to the plants. This is how genetic engineering fundamentally differs from breeding.

In genetic engineering, the DNA of plants is artificially modified through biomolecular means. DNA is a chemical contained within in all organisms' cells. It consists of a long chain of interconnected chemical bases, called nucleotides. The DNA of any specific organism contains the plans for the complete development that organism. The ability of DNA to govern development lies in the sequence of the nucleotides. Different sequences of nucleotides form genes, each of which describe the chemical structure the proteins that the cells of the organism manufactures. Genetic engineers can add new sequences of nucleotides into the natural DNA of organisms, giving them new genes which cause the cells of the organism to manufacture new proteins and exhibit traits which it would not normally possess.

New genes are introduced to plants through a process called recombination. Neil Campbell, Lawrence Mitchell and Jane Reece describe this process. In recombination, DNA not only from plants, but from any organisms including animals, can be added to the DNA of plants. First, an organism with a desirable trait is selected, and its DNA of is split into fragments using special enzymes. Bacterial DNA is also split using the same enzymes. The DNA fragment which contains the gene or genes responsible for the desired trait of the first organism is inserted into the broken bacterial DNA. The bacterial DNA, now containing foreign genes, is added to a plant cell which incorporates the foreign genes into it's own DNA sequence. The plant cell is grown in culture to produce a new plant which possesses the special trait. This new organism is called a transgenic plant (248). This method of genetic recombination allows biologists to add new genes to plants which enable them to exhibit any number of beneficial characteristics, each of which may have substantial agricultural or commercial value.

The potential of genetically modified food in agriculture is enormous. Genetic engineering allows plants to be developed with a multitude of special attributes. Some plants which have already been developed possess the ability to resist insect pests, tolerate herbicides, produce seeds with enhanced nutritional value, or manufacture pharmaceutical chemicals.

A prominent example of those plants with engineered pest resistance is Bt corn. This plant was developed to address the problem of the European Corn Borer, a widespread larval pest. To create Bt corn, explains Bernice Schacter, biologists added genes from the bacterium Bacillus thuringiensis, or Bt, to ordinary corn. Bt bacteria produce a chemical which is toxic to the corn borer. By adding genes from the bacteria to the corn, they produced a plant which naturally manufactured the same insecticide created by Bt (45). This eliminated the need for expensive insecticide application, as insecticide was always present within the tissues of the plant. With its improved pest resistance, Bt Corn offers lower losses due to insects combined with reduced cost.

Another example of applied biotechnology are herbicide-resistant plants. The purpose of these organisms is to reduce herbicide use by allowing farmers to apply a single "broad spectrum" herbicide to their crops, effectively killing any weeds of any species, but leaving the crop itself unharmed (Ho 142). This way, farmers could apply one general herbicide instead of several costly weed-specific herbicides, saving money and reducing the use of harmful chemicals.

Genetic engineering has also been used to improve the nutritional content of food. A news article by the Reuters News Agency describes one such success. A new variety of rice has been developed which produces large amounts of beta carotene, the chemical from which vitamin A is derived, within in the seeds of each plant. The scientists in charge of the project state that it is likely they will successfully develop a rice in the future which provides a day's supply of vitamin A in a single ten-ounce serving. With the new rice they intednd to help alleviate the problem of vitamin A deficiency among the children of third-world nations ("New Rice").

Because plants lack certain components of protein that are essential to human nutrition, genes for new proteins can be added to plants as a supplement (McHughen 120). The Pioneer Hi-Bred International company has added genes from brazil nuts to soybean plants (Anderson 19). The same technique could be used on any number of other plants as well.

Yet another innovative use of transgenic crops is in the production of pharmaceutical chemicals. A briefing paper written by Green Peace reveals that one company, Applied Phytologics Incorporated, is testing special transgenic rice in Sutter County, California. This rice produces several medical chemicals (1). These plants could be used to manufacture large quantities of medicines that could be synthesized in laboratories in only small amounts, or not at all. This, like other applications of biotechnology, holds great potential for the future. This potential, however, comes with a multitude of negative consequences.

Genetically engineered foods presesent tremendous risks to human health and to the environment. Foods from transgenic plants may contain any number of proteins that could cause adverse effects in humans. Genetic material from transgenic plants will escape into the environment, causing natural plants to acquire engineered DNA. This genetic pollution can cause serious environmental problems. In addition, transgenic plants both cause and encourage chemical pollution of the environment.

In the United States, two percent of adults and eight percent of children have allergies to everyday foods (Rifkin 4). Allergic reactions can be triggered by minute exposure to allergenic proteins, and the reactions can cause serious illness and even death (Anderson 19). Fortunately, people with such allergies are able to avoid food which contains elements to which they are allergic. With genetic engineering, however, plants which are typically safe can be made to produce allergenic proteins. In this way, people who consume transgenic foods may be unknowingly be exposed to allergens. This was demonstrated with the development of transgenic soybeans enhanced with DNA from the brazil nut plant. Luke Anderson explains an experiment at the University of Nebraska in which scientists took blood samples from people with a brazil nut allergy. Extracts of the transgenic soybean were added to the samples and it was discovered that if the blood donors had consumed the soy beans, they would have had severe allergic reactions (19).

The dangers of allergies extends beyond accidental exposure to typical food allergens. Because genetic engineering allows genes from any organism to be incorporated in plants, people could be exposed to a wide range of foreign proteins from genes which have never before been present in human food (Rifkin 4). Studies have shown that disease and pest resistance traits exhibited by plants are associated with the plants' allergenic properties, indicating that transgenic plants with such resistance traits are likely to be allergenic (Ho 148). Exposure to allergens is just a single hazard caused by the addition of foreign genes to plants.

Genes themselves can become harmful pollutants by spreading throughout the environment. Genetic pollution is an inevitable and uncontrollable. This spread of genes can create a myriad of problems, and numerous ways exist in which the genes of transgenic plants can be conveyed not only to plants, but to other organisms as well.

One method of transference of transgenic DNA is through cross pollination. This is where pollen from genetically modified plants fertilizes natural, non-transgenic plant species. If pollinated by transgenic pollen, a natural plant can develop offspring with the engineered traits of the transgenic plant. Genetically modified crops cannot be prevented from pollinating other plants. In a experiment conducted in Germany, researchers determined that herbicide resistance genes from a transgenic rapeseed crop can be transferred by means of cross pollination to natural crops of rapeseed two-hundred meters away (Anderson 36). In another experiment, scientists in the United Kingdom determined that transgenic rapeseed was able to pollinate five percent of the flowers of rapeseed plants more than two miles away (Anderson 49). Bees can contribute to cross-pollination between transgenic and natural plants as well. ("Pharm Crops" 2). Cross-pollination occurs between closely related species, but genes may also be exchanged between radically different organisms.

The DNA from transgenic plants can be spread by a natural process known as horizontal gene transfer. In this process, genes are exchanged between organisms that do not normally interbreed (Ho157). The genetic transfer is facilitated by bacteria and viruses in the environment (Ho 128). Through the actions of bacteria and viruses, foreign genes can be conveyed not only to other microorganisms, but more advanced life forms (Ho 179). Since 1993, scientific journals have published two hundred papers which provide evidence that horizontal gene transfer can occur between microorganisms, fungi, plants, and animals (Ho 128). Mae-Wan Ho explains one known case of horizontal gene transfer involving a gene called the mariner transposon. First discovered in fruit flies, this transposon has been found to have jumped to primates, including humans (128). Another experiment showed that laboratory rats could acquire viral DNA from viruses which they had ingested (Ho 163). The techniques used to create transgenic plants cause horizontal transfer of engineered genes to be especially likely (Ho 129). Because of cross-pollination and horizontal gene transfer, it is highly likely that DNA from transgenic plants will spread, causing adverse effects.

The consequences of pollution of the environment with transgenic DNA are severe. Luke Anderson explains that transgenic plants could contaminate the food supply by cross-pollinating with related species of food crops, causing them to manufacture chemicals which the transgenic crops were engineered to produce. Humans would then be inadvertently exposed to the drugs, pesticides and other chemicals which transgenic crops produce. Wildlife which feed on the crops would be affected as well (37). Species of weeds may acquire engineered herbicide resistance, reveals Mae-Wan Ho. This would render powerful, general herbicides ineffective, and necessitate additional applications of herbicides to eliminate the new, resistant varieties of weeds. It has been shown in Europe that weeds closely related to rapeseed have been able to acquire herbicide resistance from transgenic crops (143). If genetically engineered viral resistance was aquired by weeds , populations of species previously limited by viruses would grow unchecked (Anderson 31). Any competitive advantage aquired by weeds from transgenic crops would cause ecological catastrophy. It has already been shown that even natural plants with a competitive advantage can dramatically alter ecosystems. This is the case with European Purple Loostrife, which, since its introduction to North America, has spread unchecked, supplanting many native plant species in wetlands across the country. Experiments with tobacco plants have proven that through recombination, viruses can take viral resistance genes from transgenic plants and form new strains (Anderson 30). These new viral strains have the potential to be infectious (Ho 21). Investigations of bacterial DNA have revealed that antibiotic resistance can be and has been spread among bacteria through horizontal gene transfer (Ho 179). Genes which cause antibiotic resistance can easily be tranferred between organisms. This was illustrated in an experiment described by Luke Anderson in which seeds various transgenic crops, all engineered with antibiotic resistance genes, were added to a vessel containing a natural species of fungus. In every trial, the genes were found to have been transferred to the fungus (21). Genetic pollution will cause contamination of the food supply, create new weed species that resist pesticides and crowd out native plants, form new viruses, and encourage bacterial antibiotic resistance.

Besides polluting by genetic means, transgenic crops can cause or encourage chemical contamination of the environment. The pesticide produced within Bt crops can serve as a harmful pollutant. Bt toxin does not deteriorate when introduced to the soil, and can accumulate through repeated growth of the Bt crops in the same area (Ho 152). In the ground, the pesticide does not lose its ability to kill insects, and can potentially damage soil ecosystems (Anderson 21). Bt pesticide adversely affects benign and beneficial insect species. In Thailand, thirty percent of the bees that lived in an area surrounding a farmer's field died when Bt cotton was planted there (Ho 151). Luke Anderson describes two cases of Bt hurting insect species. In a Swiss study, lacewings were fed with corn borer larvae which had consumed Bt corn. As a result, the lacewings suffered developmental problems and increased death rates. In another study conducted in Scotland, female ladybugs were fed aphids which had preyed upon Bt potato plants. These ladybugs laid fewer eggs and lived half as long as the control insects in the experiment (29). Herbicide-resistant crops encourage the use of especially dangerous poisons in agriculture. The Monsanto company sells plants which are resistant to the broad-spectrum herbicide "Roundup", which consists primarily of the chemical glyphosate, as explained by Mae-Wan Ho. The US Fish and Wildlife Service has determined this chemical to be harmful to seventy-four endangered plant species. In addition, glyphosate is toxic to earthworms, mycorrhizal fungi, and nitrogen-fixing bacteria, all of which are essential to soil ecosystems (142). It has been determined that glyphosate kills fish in concentrations as low as ten parts per million, and can cause several illnesses in humans (Anderson 24). The chemical is also water soluble, and can easily pollute groundwater (Anderson 24). Genetically engineered crops cause or encourage the release of harmful chemicals, and threaten both human health and the environment.

Genetic engineering in agriculture has great potential both as a tool and as an environmental threat. Genetically engineered crops already significant advantages over traditional crops. Biologists have succeeded in creating new crops which require no pesticide or allow the application of powerful herbicides to eliminate all weeds with a single spraying. There are new crops with extra beta carotene and protein, and even plants which produce medicines. At the same time, transgenic crops will create a multitude of problems. Transgenic food can provoke allergies. the new enhanced crops will create a kind of genetic pollution which can expose humans and animals to strange chemicals, create hardier weeds that can resist herbicides or even crowd out native plant species, create new viruses and encourage antibiotic resistance among bacteria. In addition, transgenic crops are a cause of chemical pollution in the environment, harming insects, plants, soil, fish and even humans. Genetic engineering may hold promise, but the risks are far to great. By continuing to use genetically engineered crops, the world continues to contribute to these dangers, and therefore, the further development and planting genetically engineered crops must be banned.

Works Cited

Anderson, Luke. Genetic Engineering, Food, and Our Environment.
Vermont: Chelsea Green, 2000.

Campbell, Neil, Lawrence Mitchell, and Jane Reece. Biology: Concepts and Connections. 3rd ed.
SanFancisco: Addison Wesley Longman-Benjamin/Cummings, 2000.

Ho, Mae-Wan. Genetic Engineering: Dream or Nightmare?.
New York: Continuum, 1999.

McHughen, Alan. Pandora’s Picnic Basket: The Potential and Hazards of Genetically Modified
Foods. New York: Oxford University, 2000.

"New Rice Could Save Lives: Scientists Create Golden Rice With More Vitamin A." 2000.
Reuters. 13Nov. 2001 http://abcnews.go.com/sections/science/DailyNews/rice000113.htm.

"Pharm Crops--A Food Accident Waiting to Happen." Sep. 2001.
GreenPeace. 20 Sep. 2001 http://www.greenpeaceusa.org/media/publications/pharm_rice.pdf.

Rifkin, Jeremy. "Genesis II." Across the Board. Jun. 1998: 29-35. Science 1999. Ed. Eleanor
Goldstein. Boca Raton, FL: SIRS Mandarin, Inc., 1999. Art. 73.

Schacter, Bernice. A Reference Guide: Issues and Dilemmas of Biotechnology.
Connecticut: Greenwood, 1999.

Copyright © 2001 by Ryan Shon